This invention relates to an apparatus for notching an edge of an elongated web, particularly (but not exclusively) for notching a longitudinal edge of a strip of photographic film.
Equipment of the general type here under discussion is used in the photographic field for various purposes. For example, in modern film-processing laboratories it is customary to develop a whole series of films (each film may come from a different customer) and thereafter to connect the individual films endwise so as to form a long (composite) strip of film which is then passed through automated copying machinery (a printer). In preparation for this printing operation the equipment here under discussion may be used to form in a longitudinal edge of the long film strip a notch opposite each film frame to be copied; these notches are then sensed and thus serve to control the operation of the printer and/or associated devices, e.g. to determine where the respective film frame must be located before printing begins. Another use of such equipment is to form film strip edges with notches which then serve (e.g. in a press-splicer) to identify where film strips (or sections thereof) are to be spliced together.
According to a prior-art proposal the film strip(s) is (are) photoelectrically scanned to determine where the blank (transverse) film portions are located which separate successive film frames from one another. Whenever one of these portions is sensed, a signal is generated which triggers operation of the notching equipment. The notching itself is usually performed by a reciprocating die or punch.
This type of equipment is no longer suitable for today's high-performance photo-finishing installations. The operations of the devices used in such installations e.g. photo-electric scanners, splicers, printers, and the like) can all be carried out at high speed, a factor which is essential both for economic reasons and to meet the customer demand for quick return of the developed and printed film. The speed of operation of these devices is, however, limited by the slowest operation in the chain: the time required for producing the notches because the notching equipment requires for each operating (notch-forming) cycle a time interval which is composed of the times for the reciprocation of the punch between its operative and retracted positions. If it were not for the delay resulting from this aspect, the photo-finishing operation (of which the notching is only one part, as indicated above) could proceed much faster.
Another objectionable aspect of notch-forming by means of reciprocating punches is that tacky adhesive tends to cling to the punch when a notch is formed (purposely or otherwise) in a splice, i.e. where two film strips are connected by the (adhesive) splice.